Hard starting brain trust question.. Options

[oakdalecurtis]

- 76 2.0, fuel injected, stock except for Crane Fireball ignition.
- Owned for 30 years, starts and runs flawlessly
- Optima Red Top battery kept in top trickle charged condition
- Alternator working perfectly
- 4 years ago I replaced to starter relay with the 6v Ford relay modification to stop hard hot starting issues
- Still, if car is stalled after running up to temp, attempting restart can be difficult. Engine will barely crank over, if at all, until allowed to cool down. Not sure where to begin to look for a fix. Fuel pump is under gas tank so I don’t think it can be any kind of vapor lock. If engine allowed to sit and cool a bit, the battery has plenty of cranking power then to start car right up.
- Not sure what to look at next to get reliable hot starts…
What say the brain trust here???

[FlacaProductions]

Grounds clean and tight - especially the transmission ground?

[oakdalecurtis]

Grounds clean and tight - especially the transmission ground?

hi Flaca,
Yes, grounds are all checked and good, as evidenced by easy fast start when not hot too.
Could a warm engine change a good ground to a poor ground regularly?

[FlacaProductions]

Resistance rises when things get hot(ter) so it's a shot. I'd make sure your + is good to go - they do decay from the inside so what looks ok from the outside with a cursory check may not tell the true story.

check this as well:
http://www.914world.com/bbs2/index.php?s=&...t&p=2720014

[oakdalecurtis]

Resistance rises when things get hot(ter) so it's a shot. I'd make sure your + is good to go - they do decay from the inside so what looks ok from the outside with a cursory check may not tell the true story.

check this as well:
http://www.914world.com/bbs2/index.php?s=&...t&p=2720014

Ty Flaca, will check grounds.....

[Superhawk996]

Grounds clean and tight - especially the transmission ground?

hi Flaca,
Yes, grounds are all checked and good, as evidenced by easy fast start when not hot too.
Could a warm engine change a good ground to a poor ground regularly?

Grounds - what does checked and good mean? Not enough to simply tighten a ground strap if the strap itself is the source of the high resistance ground.

Ground strap connection needs to be Zero Ohms. 0.1 ohms is not acceptable, it must be zero. Most multimeters will struggle to read accurately at these low resistance levels. The best way to measure is to measure the voltage drop across the ground strap while the engine is cranking. If you have any voltage being dropped across the ground strap it should be replaced.


Could a ground strap go good to bad when hot - absolutely

Resistance increases with temperature as stated above

Edit: I know I’m focused on the body to trans ground strap since that is where the problems usually originate but I’ve also repaired one instance where the high resistance was coming from the battery negative cable and it’s connection to chassis ground.

[mgphoto]

- 76 2.0, fuel injected, stock except for Crane Fireball ignition.
- Owned for 30 years, starts and runs flawlessly
- Optima Red Top battery kept in top trickle charged condition
- Alternator working perfectly
- 4 years ago I replaced to starter relay with the 6v Ford relay modification to stop hard hot starting issues
- Still, if car is stalled after running up to temp, attempting restart can be difficult. Engine will barely crank over, if at all, until allowed to cool down. Not sure where to begin to look for a fix. Fuel pump is under gas tank so I don’t think it can be any kind of vapor lock. If engine allowed to sit and cool a bit, the battery has plenty of cranking power then to start car right up.
- Not sure what to look at next to get reliable hot starts…
What say the brain trust here???

Dump the Ford solenoid it’s a bandaid, your Bosch solenoid gave up four years ago, get a new starter.
Problem is cost, rebuilt Bosch is pricey but you will get maybe 3 to 4 years on a Brazilian solenoid (not racist, quality control and corporate greed) then it’s back to the same problem.
Get the hi torque starter, it’s based on the Toyota starter, which is easily rebuilt.
I’m not sure about your ignition system, there could be something that isn’t configured correctly. Best solution is the 123 distributor, you won’t look back.

[oakdalecurtis]

Took room’s advice, got under the car today and removed ground strap to transmission.
(the tranny nut was a pia…)
I was surprised at the amount of hard grease that had accumulated on both ends of the strap connections! Cleaned everything up, added a dollop of dielectric grease and reassembled everything. I haven’t had a chance to run it to hot and test it, but I have no doubt you all hit on the problem. I love this forum! (IMG:style_emoticons/default/piratenanner.gif)

[r_towle]

Get a brand new 3-4 foot ground strap at the parts store .
Get one with bolt holes on both ends.
One goes to the battery, gets routed around the back of the engine bay.
Bolt the other end to the upper starter bolt.
Now you have solid ground to the starter.
All hidden.

[oakdalecurtis]

Get a brand new 3-4 foot ground strap at the parts store .
Get one with bolt holes on both ends.
One goes to the battery, gets routed around the back of the engine bay.
Bolt the other end to the upper starter bolt.
Now you have solid ground to the starter.
All hidden.

Hey towle,
I always wondered why the didn’t just run a ground directly to the starter, instead of a convoluted trunk to tranny approach, but it was probably simpler and cheaper…

[930cabman]

Is your starter OK, might want to pull it and have it tested. Bushings may be loose and open up after warm up

[Superhawk996]

I always wondered why the didn’t just run a ground directly to the starter, instead of a convoluted trunk to tranny approach, but it was probably simpler and cheaper…

The reason this isn’t done is because it will basically double the voltage drop due to cabling. You want the voltage drop in cables minimized and as close to zero as you can by keeping cables as short as possible.

Here’s the math:

4 gauge battery cable is about 0.2533 ohms per 1000 feet at 70 degrees F.

0.2533 / 1000 = 0.0002533 ohms per foot

0.0002533 ohms per foot x 4’ cable = 0.00010132 ohms for the 4’ negative cable not counting resistance at the connections to sheet metal.

Average 4 cylinder starter draw is about 150 amps - can be higher when cold and trying to crank a motor using thick oil.

Voltage drop = amps x resistance
150 amps x 0.00010132 ohms= .152 volts dropped in that single ground cable when everything is perfectly new.

It is far better to use only a 6 - 8” negative ground strap between the body and engine/trans to cut that voltage drop down to almost zero.

A 0.152 volt drop in the negative cable doesn’t sound like much but remember you also have about the same cable length on the positive side for a total of 0.3 volts lost in cabling. This is not insignificant. Likewise this voltage drop will only get worse over time as the cable and the end connections corrode. Temperatures in and around the engine will increase resistance of the cable over ambient. And a starter working hard and pulling higher amperage will drastically increase it.

That is why OEMs don’t run negative cables all the way to the starter. Nothing to do with cost. Has everything to do with ensuring the system has minimal voltage drop and starts reliably.

[r_towle]

That worked soooooo well using a braided ground strap.

[oakdalecurtis]

I always wondered why the didn’t just run a ground directly to the starter, instead of a convoluted trunk to tranny approach, but it was probably simpler and cheaper…

The reason this isn’t done is because it will basically double the voltage drop due to cabling. You want the voltage drop in cables minimized and as close to zero as you can by keeping cables as short as possible.

Here’s the math:

4 gauge battery cable is about 0.2533 ohms per 1000 feet at 70 degrees F.

0.2533 / 1000 = 0.0002533 ohms per foot

0.0002533 ohms per foot x 4’ cable = 0.00010132 ohms for the 4’ negative cable not counting resistance at the connections to sheet metal.

Average 4 cylinder starter draw is about 150 amps - can be higher when cold and trying to crank a motor using thick oil.

Voltage drop = amps x resistance
150 amps x 0.00010132 ohms= .152 volts dropped in that single ground cable when everything is perfectly new.

It is far better to use only a 6 - 8” negative ground strap between the body and engine/trans to cut that voltage drop down to almost zero.

A 0.152 volt drop in the negative cable doesn’t sound like much but remember you also have about the same cable length on the positive side for a total of 0.3 volts lost in cabling. This is not insignificant. Likewise this voltage drop will only get worse over time as the cable and the end connections corrode. Temperatures in and around the engine will increase resistance of the cable over ambient. And a starter working hard and pulling higher amperage will drastically increase it.

That is why OEMs don’t run negative cables all the way to the starter. Nothing to do with cost. Has everything to do with ensuring the system has minimal voltage drop and starts reliably.

Wow Superhawk! That was a great explanation of why not do what seemed like an obvious fix!

[ClayPerrine]

I use braided ground straps from the transmission to the body, and from the body to the negative battery post. I also make sure the places they bolt are spotless bare metal so they have the lowest resistance. On all three cars I stopped using the stud welded to the underside of the trunk, and started using one of the trans mount to body 8mm bolts. I could never make sure that stud was clean and shiny.

On the big six, I also added a ground lead from the right front cam carrier to the ground post on the body where the braided battery cable attaches.

And one last thing. Every time I disconnect a ground connection anywhere on a 914, I clean both the wires and the mounting points until they are bright and shiny.

[r_towle]

On the big six, I also added a ground lead from the right front cam carrier to the ground post on the body where the braided battery cable attaches.

That step imho is the key.
Not sure where a decent place is. But a short cable to the case, right next to the battery, makes sense.

I will admit that after I put in two new ,yes two, braided ground strap, my slow starter went away.

Fun fact, go google slow starter on a 997.
They still seem to disobey the rules.

[Superhawk996]

That worked soooooo well using a braided ground strap.

Don’t mistake 50 year old hardware that hasn’t been routinely maintained and in poor condition for poor design. Many of these cars still have the original ground straps and still function as intended - a testament to solid design practice.

Braided ground strap is superior to stranded cable in this application between a rigid body and an engine / transmission that is vibrating and has movement on rubber engine and trans mounts.

Braided ground strap has more flexibility to resist mechanical stress and fatigue.

Braid dissipates heat better than insulated cable. Pulling 100 - 200 amps through anything other than a zero ohm wire will generate heat - especially under extended cranking.

Braided ground strap also supports higher amperage’s than a similarly sized stranded cable with larger diameter strands.

[r_towle]

My car was all updated.
I read quite a bit about braided ground straps failing due to corrosion, but I’m certain you have an answer for that too.

I just deal in factual results, not theory.

A ground cable to the starter bolt works great.
A ground cable to the engine directly from the battery works great.
Doubling up ground straps works.

Obviously, cleaning all connections matters.
Obviously, based upon many 997 threads, which are 2005-2012 era, Porsche still seems to not understand electrical theory and slow start (melting cables and connectors) is not the fault of bad design….sure.

[930cabman]

Do you have the ability to check the amperage draw while cranking?

My $5. is on this culprit

[oakdalecurtis]

One final question on this hard starting issue. As I mentioned, I completely cleaned the ground strap connections, which were dirty, and suspect that will clear up the issue. My question is, the original strap is in one piece, but does look old. Can age alone increase the resistance on an intact braided wire? If so, anyone know where I can get a new one?